Using Mendel's flower color (purple is dominant, white is recessive), if two heterozygous plants are crossed, what is the probability that the first two offspring will have purple flowers?
A) 1/2
B) 1/4
C) 6/4
D) 9/16
E) 1/16

Question

Quizplus · Accepted Answer

When two heterozygous plants are crossed, their genotypes are both Pp. This means that each parent has a 1/2 chance of passing on either the dominant P (for purple) or the recessive p (for white) to their offspring. To determine the probability of the first two offspring having purple flowers, we need to use a Punnett square.

PP   Pp
Pp   pp

Each box represents a potential offspring, with the letters representing the alleles they could receive from each parent. From this Punnett square, we can see that there are four possible combinations of alleles that result in purple flowers: PP, Pp, Pp, and pp. However, since we only care about the probability of the first two offspring having purple flowers, we only need to look at the first two boxes in the square.

The probability of the first offspring having purple flowers is 3/4 (since there are three ways out of four for it to get a P allele). The probability of the second offspring having purple flowers is also 3/4. We can multiply these probabilities together to get the overall probability of both offspring having purple flowers:

3/4 x 3/4 = 9/16

Therefore, the answer is D: 9/16.

Using Mendel's Flower Color (Purple Is Dominant, White Is Recessive)